Knife-clamping device



P. S. 'MITTS KNIFE GLAMPING DEVICE Filed March 9, 1923 INVENTOR Y ATTORNEY llllllll Patented Ben. 23, I924.

rants PHILIP S. MITTS, 0:? SAGINAW, MICHIGAN, ASSIGNOR TO MI'ITS & MERRILL, A COR- PORA'IION OF MICHIGAN. i

KNIFE-CLAMPING DEVICE.

Application filed March a, 1923. Serial No. 626,142.

To 64% whom it may concern:

Be it known that I, PHILIP S. Mrr'rs, a citizen of the United States, residing at Saginaw, in the county of Saginaw and State of Michigan, have invented certain new and useful Improvements in Knife- Clamping Devices; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention is an improved knifeclamping device for securing cutter knives to the cylindrical drum of a cutting machine of the type commonly known as a hog.

Some substances are extremely hard to shred or disintegrate by ordinary shearing methods. In shredding machines in which rotary drums and cutting knives are used difficulty has been experienced in mounting the knives rigidly enough to prevent their being displaced when encountering the resistance of the material. Some disintegrating machines known as sawmill hogs have usually been of large diameter and relatively short axial length, because sawmill refuse does not require the use of exceptionally long cutting drums.

In adapting machines of the sawmill hog type to the cutting of other substances it has been found desirable to make the drums of considerable axial length, say, about four feet,to take in wide material, such as wide veneer refuse, etc.

Heretofore it has been customary in largediameter short cylinder machines, such as the sawmill hogs referred to, to attach the knives to the rotary drum by inserting the knives and bolting them in place by a wrench operated from inside the revolvable drum.

However, this method of fastening from inside the drum is feasible only whenxthe drum is of relatively large diameter and short enough axially to allow the operator to fasten the knife bolt by reaching inside the drum from one end. When a drum of considerable axial length is used, such as is now required for the class of wide work mentioned, the knife-clamping bolts near the middle of the length of the drum can not be readily reached from the end of the drum. Consequently in adapting long drums it has been found essential to devise some method of inserting the knife and securing it rigidly from outside.

To fasten knives rigidly on the drum andavoid their displacement when subjected to hard usage I have found it advantageous to provide means for springing or bowing the body of the knife against a concave or. a convex seat within the drum shell, so that by reason of the curved or bowed surface the been sprung or bowed, but sofar as I am aware no means has ever been provided in practice whereby the knife has been so mounted on the drum that it can be bolted in place from outside the drum and is also sprung and bowed against a curved seat in the drum.

A purpose of my present invention is, therefore, to provide means for so securing the knives of a drum-type cutter that the knives can be readily fastened to a drum regardless of the drums axial length and the knife can also be bowed against a concave or a convex seat thereby absolutely locking the knives against displacement while the machine is in use.

l Vith the foregoing and certain other ob jects in view which will be described later in the specification, my invention comprises the devices described and claimed and the equivalents thereof.

In the drawmgs, Fig. 1 1s a side View,

partly broken away, showing a drum with,

for bowing the knife in the direction opposite that shown in Fig. 1.

Fig. 3 is a front view showing the knife as seen from the direction indicated by the arrow in 1.

Fig. 4. is a modified form of knife tapered rearwardly.

Fig. 5 is a further modified form of the knife tapered forwardly.

Fig. 6 is a plan View of the knife with part of its surface roughened.

against being driven back.

As is clearly shown in the drawings, 1 indicates the usual revolvable drum of a cutting machine or hog of the class described, 2 is the knife adapted to be received within a knife pocket 3 formed in the drum. Above the knife pocket 3 is a socket 4.see Figs. 2 and 3which receives the bolt or machine screw 5 by which the knife is secured to one face 6 of pocket 3.

The end of screw 5 is threaded into a clamping plate 7 received in pocket 3. This clamping plate is preferably of substantially the same length as said bearing face 6.

Clamping plate 7 may have a convex upper surface 8, as shown in Fig. 1, or it may have a concave upper surface 9, as shown in Fig. 2. Similarly the wall 6 of the pocket '3 may be concave, as shown in Fig. 1, or convex, as shown in Fig. 2. In either construction the knife 2, which is received between the curved face 6 of pocket 3 and the correspondingly curved face of damp ing late 7, will be bowed or bent as indicate in Fig. 1 or Fig. 2 by tightening the clamping screw. Bowing the plate effectually looks it against being driven back by blows from outside, such as would be produced: by the cutting resistance of some materials. The long curve-faced clamping plate 7 when drawn tight against the knife binds the knife at the middle where the bolt is located and also at the ends of the long bearing surface 6.

To facilitate removal of the knife from the drum 8 I prefer to form the top of the pocket 3 with a groove or channel 10see Figs. 2 and 3adapted to admit a hook 11 by which the knife 2 may be easily withdrawn from its pocket after having been released by the clamping plate 7.

The plate 7 is additionally held in its proper position in the pocket by a downwardly projecting lug 13 that engages a shoulder 14 on the drum rim. The outer face of this lug 13 thereby becomes an impinging surface to take the impact of the cut material. It also prevents chips entering the drum. This face is preferably slightly concaved as shown in Fig. 1, to deflect or turn the chips. When the face of lug 13 becomes worn the plate 7 can be easily renewed.

For certain uses I may construct the knife as in Fig. 4, where the blade is shown tapered, that is, it may be of less thickness at the back end than. at the front or cutting end. The taper, in addition to the bowing of the knife, which I have indicated by a dotted line, effectually locks the knife In some cases where extremely high drum speed is used,.it may be desirable to taper the knife in the opposite direction, that is, to make it thicker at the back than at the front as in Fig. 5 to more securely hold the knife against being thrown out of position by centrifugal force.

In addition to bowing the knife and in some cases, tapering it as shown in Figs. 4 and 5, I may also roughen the surface of the knife by leaving tool marks on its surface, as indicated in Fig. 6, to increase the grip between the knife surface and the clamping plate 7 and between the knife surface and the face of the pocket 3.

By the means above described I have pro vided a simple yeteffective and extremely rigid clamping device whereby knives can be quickly and accurately assembled in the drums of cutting machines. This device makes it possible to use a knife drum of unusual axial length adapted for cutting extremely wide materials, because the knife is inserted and fastened by means operated from outside the drum, making it unnecessary to reach into the drum in order to insert knives near the middle of the length of the drums as heretofore. The device has also the very important practical advantage, aside from enabling the knife to be secured in place by a bolt inserted from the outside, of enabling the knife to be sprung from outside the drum.

Springing or bowing the knife by means of a curved plate or its equivalent within the drum, and actuating the plate by tightening devices operated from outside the drum is a novel and extremely useful feature of my present invention, for it enables knives to be easily and quickly secured to a drum even though the drum be of unusual axial length.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a shredding machine drum, a knifeclamping device comprising a knife-receiving pocket in the periphery of said drum, a wall of said pocket curved, a clamping plate having a correspondingly curved face, a shredding knife received between the said curved wall of the pocket and the curved face of said clamping plate, an end of said clamping plate extending to and forming a closure for said knife-receiving pocket at the periphery of the drum, a bolt-socket formed in the exterior periphery of said drum, a bolt in said socket, an end of said bolt engaging said clamping plate, said bolt adapted when tightened from within said socket to clamp and bend said knife.

2. In a shredding machine drum, a knifeclamping device comprising a knife-receiving pocket in the periphery of said drum, a wall of said pocket curved, a clamping plate having a curved face, a shredding knife received between the curved wall of said pocket and thecurved face of said clamping plate, a bolt-socket formed in the exterior periphery of said drum, a bolt in said socket, an end of said bolt engaging said plate, said bolt adapted when tightened from within said socket to bend and clamp said knife, a lug on the outer edge of said clamping plate, and a shoulder on said drum adapted to be engaged by said lug.

3. In a shredding machine drum, a knifeclamping device comprising a knife-receiving pocket in the periphery of said drum, a Wall of said pocket curved, a clamping plate having a curved face, a shredding knife received between the curved wall of said pocket and the curved face of said clamping plate, an end of said clamping plate extending to and forming a closure for said knifereceiving pocket at the periphery of the drum, a bolt socket formed in the exterior periphery of said drum, a bolt in said socket, an end of said bolt engaging said clamping plate, said bolt adapted when tightened from outside the periphery of the drum to bend and clamp said knife, and a laterally extending groove formed in the curved wall of said. pocket and extending from the periphery of the drum inwardly toward the bolt socket.

4C. In a shredding machine drum, a knife clamping device comprising a knife-receiv- 7 ing pocket in the periphery of said drum, a wall of said pocket curved, a clamping plate having a curved face, a shredding knife received between the curved wall of said pocket and the curved face of said clamping plate, a bolt-socket formed in the exterior periphery of said drum, a bolt in said socket, an end of said bolt engaging said clamping plate, said bolt adapted when tightened from outside the periphery of the drum to bend and clamp said knife, a lug on said clamping plate, the outer face of said lug concaved and a shoulder on said drum adapted to be engaged by an inner face of said lug.

In testimony whereof, I afliX my signature.

PHILIP S. MITTS. 

